Sandy Lake (Bedford, NS) limnological profiles reveal freshening and oxygenation of the water column after extreme rain events; and a worrisome “Metalimnion Oxygen Minimum” 2Sep2023

By the outlet on Sandy Lake, Aug 14, 2023. Insets: At left the YSI Probe with weight attached; right: YSI Instrument panel. A portion of the Van Dorn water sampling bottle can be seen by the anchor.
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After  extreme precipitation events earlier in the summer of 2023, the entire  water column had lower conductivity values ( a measure of salt content) on Aug 14 compared to May 22  and bottom waters on Aug 14 were better oxygenated than on 6 other occasions in the past when deep water oxygen levels were measured in late summer/early fall. This flushing and oxygenation could be good news if there weren’t other adverse effects of the heavy precipitation. Observations in the latter half of August in 2021, 2022 and 2023 show the presence of a “Metalimnion Oxygen Minimum” at 5-6 m; it appears that it reformed quickly after the high precipitation events in 2023.  The occurrence of a Metalimnion Oxygen Minimum in Sandy Lake represents significant deterioration in water quality of the upper layers of the water column and  adds yet more reason to be concerned about the state of the lake currently and the possible impacts on lake water quality if the proposed major development on its headwaters was to proceed.
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